Failed to connect to security.ubuntu.com port 443: Connection refused

# apt-get install curl        
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following NEW packages will be installed:
  curl
0 upgraded, 1 newly installed, 0 to remove and 9 not upgraded.
Need to get 139 kB of archives.
After this operation, 340 kB of additional disk space will be used.
Err:1 https://security.ubuntu.com/ubuntu xenial-security/main amd64 curl amd64 7.47.0-1ubuntu2.14
  Failed to connect to security.ubuntu.com port 443: Connection refused
E: Failed to fetch https://security.ubuntu.com/ubuntu/pool/main/c/curl/curl_7.47.0-1ubuntu2.14_amd64.deb  Failed to connect to security.ubuntu.com port 443: Connection refused

E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?